My own adopted DD was fostered for 6 weeks before we got her. Funnily enough, she doesn't have the slightest interest in tracing her birth parents, who were very young, and apparently were bullied into adoption, which was so often the sad case 50 years ago. It's quite likely that they stayed together, and she may have siblings. I would love to find her family, but it's not going to happen.
We went on to do short-term fostering of under 5s. Many of them came from rather dubious families, and were borderline for going into care. I often wonder what became of them all. It's lovely that one of your babies has found you, after all these years. Enjoy your reunion!